Abstract

Many hearing aids introduce compressive gain to accommodate the reduced dynamic range that often accompanies hearing loss. However, natural sounds produce complicated temporal dynamics in hearing aid compression, as gain is driven by whichever source dominates at a given moment. Moreover, independent compression at the two ears can introduce fluctuations in interaural level differences (ILDs) important for spatial perception. While independent compression can interfere with spatial perception of sound, it does not always interfere with localization accuracy or speech identification. Here, normal-hearing listeners reported a target message played simultaneously with two spatially separated masker messages. We measured the amount of spatial separation required between the target and maskers for subjects to perform at threshold in this task. Fast, syllabic compression that was independent at the two ears increased the required spatial separation, but linking the compressors to provide identical gain to both ears (preserving ILDs) restored much of the deficit caused by fast, independent compression. Effects were less clear for slower compression. Percent-correct performance was lower with independent compression, but only for small spatial separations. These results may help explain differences in previous reports of the effect of compression on spatial perception of sound.

Received 05 October 2012Revised 13 February 2013Accepted 14 February 2013Published online 03 April 2013

Acknowledgments:

Many thanks to the researchers at Starkey Hearing Research, Berkeley, CA, including Sridhar Kalluri, Olaf Strelcyk, Jing Xia, Brent Edwards, Nazanin Nooraei, and Joyce Rodriguez for helping to create the original hypotheses that drove this work and for creating a better understanding of the practical context and implications of this research. Thanks also to Tim Streeter and Scott Bressler for setting up and running the HRTF measurements, and to Justin Fleming for work contributing to the analysis of temporal offsets on performance. This work was supported by Grant No. NIDCD ROI DC009477.